Research On Data Acquisition System Of HIAF Beam Intensity Detector Based On ZYNQ

High Intensity Heavy-ion Accelerator Facility(HIAF)is one of the"12th Five-Year Plan"key construction items determined in the"National Medium-term and Long-term Plan for Major Scientific and Technological Infrastructure Construction(2012-2030)".It will be a next generation of high-intensity heavy-ion accelerator device with leading international level.HIAF integrated accelerator system,experimental terminal system and supporting facilities is a leading multi-disciplinary heavy ion scientific research device,which provides an advanced experimental platform for the application of heavy ion beam.The beam intensity measurement system is an important part of the accelerator,which provides the intensity information of each location of the accelerator for researchers.The intensity measurement system is composed of beam probe,front-end electronics and data acquisition system.Taking single-wire detector as an example,heavy ion beams impinge on a gold-plated tungsten wire with a diameter of 50 microns,the charges of particles accumulate on the single wire and output weak current signals,which reflects the beam intensity at the location of the single wire.When measuring a beam of 100 u A,the maximum current output from the detector is 1 u A～1.5 u A,the output current is 1/100 of the beam intensity.The output signals of the accelerator beam intensity detector have the characteristics of low current intensity and large dynamic range.This paper designed a beam intensity data acquisition system based on Xilinx FPGA(Field Programmable Gate Array)for HIAF,which includes front-end electronics,calibration current source,analog-to-digital conversion circuit,digital signal processing circuit and corresponding power supply circuit.The system uses a programmable Trans-Impedance Amplifier(TIA)and Bessel filters to convert and amplify the weak current signal from single-wire detector;18 bit high precision ADC(Analog to Digital Converter)converts analog signals to digital signals;The functions of digital filters,system control,network communication,multi-channel triggering are implemented by programs deployed on Xilinx XC7Z015 chip(ARM+FPGA SOC,System on Chip).This system not only supports scientific researchers to measure the beam intensity of accelerators remotely,but also interlocks with other devices on the accelerator to trigger sampling,trigger output and so on.Through reasonable functional distinction and layout,the system in a 14cm×20cm printed circuit board implements the function of multiple devices of the traditional beam intensity data acquisition system.In this paper,the application background and significance of the beam intensity data acquisition system are introduced in the first chapter.In the second chapter,the commonly used beam intensity measurement methods at home and abroad are introduced.Based on the parameters of HIAF,the corresponding technical parameters for electronics are given,and the system design scheme is determined.The third chapter describes the hardware design of the system in detail:the noise source analysis and calculation are made for the front-end electronics,the Low Dropout Regulator(LDO)circuit and front-end control circuit matched with the sampling circuit are designed.Through the analysis of the working principle of ADC chip,the appropriate ADC chip is selected according to the requirements of interface,anti-jamming ability,sampling accuracy,sampling speed,etc.According to the computing power and functional requirements,we selected the chip and external interface,and designed the matching power supply circuit.The fourth chapter mainly introduces the software design of the system:we deployed ADC driver program,front-end electronic control program,FIR(Finite Impulse Response)filter and noise reduction program in the programmable logic part of ZYNQ,and deployed embedded Linux operating system and LWIP(Light Weight IP)network communication protocol in the processing system part.Front-end electronics and ADC chip collect and convert analog signals under the control of digital circuits.Data are filtered and de-noised locally and uploaded to the host computer via Gigabit Ethernet.Finally,in the fifth chapter,the function validation and performance test of the system are carried out.Test results show that the system can achieve the expected functions and meet the parameters of single-wire detector.In the sixth chapter,a brief summary is made,the innovations of this system compared with the traditional beam intensity measurement system are pointed out,the shortcomings exposed by experiments are analyzed,and the next phase improvement plan and suggestions are planned.The test results show that the system functions normally,the front-end amplifier achieves 100 times to 10~8 times adjustable signal gain,the input current signal ranges from 40p A to 4m A,the sampling rate is 1Msps,and the Integral Nonlinearity is0.185%,which meets the beam intensity measurement requirements.The focus of the next stage is to increase the sampling rate of the ADC and reduce the background noise of the circuit.There are three main innovations in this work:Firstly,compared with the traditional beam intensity measurement system with multi-plate structure,this system integrates front-end electronics,calibration current source,analog-to-digital conversion circuit and data processing module on a printed circuit board to achieve double compression of volume and power consumption.Second,compared with the fixed gain front-end electronics and low-bit ADC chips used in the traditional intensity measurement system,this system improves the quality of signal acquisition and enlarges the dynamic range with variable gain preamplifier,high-precision ADC chip and anti-jamming methods.Third,the software and hardware of the system are self-developed products,which have better scalability and upgrade potential than the traditional beam intensity measurement system using commercial equipment.